The El Segundo-based organization said that an examination had revealed the dolphin died from a gunshot wound. It is offering a $5,000 reward for information that leads to the conviction of the person who shot the animal.

Marine Animal Rescue
The dolphin, found floating in the surf in Manhattan Beach, California, died from a gunshot wound.

Marine Animal Rescue founder Peter Wallerstein told NBC News that he got a call last week from someone who spotted the dolphin floating in the surf. He retrieved the animal’s body and then contacted authorities in the hopes of opening an investigation into who did this, although he admitted that “we very rarely find these people.”

Wallerstein told BuzzFeed News that his organization frequently sees sea lions that have been shot because they steal bait off boats and otherwise interfere with fishing. But dolphins, he said, generally don’t interfere with fishing, and he can’t imagine why someone would shoot one. It’s an “act of brutality,” he said.

Earlier this year, a similar incident in Mississippi made headlines when a pregnant dolphin was found fatally shot on a beach in April. The unborn calf did not survive. Federal authorities announced in July that they were looking for information on whoever was responsible.

Since dolphins fall under the Marine Mammal Protection Act of 1972, a person found responsible for killing one could face up to $100,000 in fines and one year in prison.

Although Wallerstein noted that dolphins normally don’t interfere with humans fishing, the National Oceanic and Atmospheric Administration said in July that the wild animals sometimes learn this kind of behavior when people feed them. That teaches them to start approaching boats in search of food, which can lead to conflict with fishermen.

NOAA believes this may be the reason for an apparent uptick in human violence against dolphins in the Northern Gulf of Mexico region in recent years.